Sieverts's law, inphysical metallurgy and inchemistry, is a rule to predict thesolubility ofgases inmetals. It is named after German chemistAdolf Sieverts (1874–1947).^[1] The law states that the solubility of adiatomic gas in metal is proportional to the square root of thepartial pressure of the gas inthermodynamic equilibrium.^[2]Hydrogen,oxygen andnitrogen are examples of dissolved diatomic gases of frequent interest in metallurgy.

Sieverts's law can be readily rationalized by considering the reaction of dissolution of the gas in the metal, which involvesdissociation of the molecule of the gas. For example, for nitrogen:

N₂ (molecular gas) ⇌ 2 N (dissolved atoms)

For the above reaction, theequilibrium constant is

${\displaystyle K=\frac{c_{\text{at}}^2}{p_{\text{mol}}},}$

where:

c_at is the concentration of the dissolved atoms into the metal (in the case above, atomic nitrogen N),

p_mol is the partial pressure of the gas at the interface with the metal (in the case above, the molecular nitrogen N₂).

Therefore,

${\displaystyle c_{\text{at}}=\sqrt{K{p}_{\text{mol}}}.}$

• Henry's law
• Graham's law

• Metallurgy
• Materials science

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